A new way to chill out is simple: Just unwind.
Called twistocaloric cooling, the method involves unwinding tightly twisted strands of various materials. The technique was used to chill water by several degrees Celsius, scientists report in the Oct. 11 Science.
Cooling techniques like those used in traditional refrigerators rely on cycles of compressing and expanding gases. But those gases can contribute to global warming (SN: 10/25/16). So researchers have been looking for alternative cooling methods based on manipulating solid materials. Consider a rubber band: When stretched, it heats up, becoming warm to the touch. When released, it cools down. The same goes for twisting and untwisting.
To study this effect, a team of scientists from China, the United States and Brazil twisted fibers of rubber, fishing line and wires made of a nickel and titanium alloy. When twisted tightly enough, the various types of strands formed coils or even supercoils — coils of coils. Unwinding a stretched, supercoiled rubber fiber cooled its surface by as much as 15.5 degrees Celsius.
Unraveling cables made of several strands twisted together produced cooling as well. But simply cooling the strands isn’t particularly useful. So the researchers created a “twist fridge” that could chill water. Unwinding a three-ply, nickel-titanium cable while flowing water over it dropped the liquid’s temperature by nearly 8 degrees C, the team reports.